Power reception device and electronic apparatus

Abstract

A power reception device includes a power reception antenna, a rectifier circuit, a communication section, a switch and a switch control section. The rectifier circuit converts electric power received by the power reception antenna into direct current voltage. The communication section communicates via the power reception antenna. The switch is connected between the power reception antenna and the communication section. The switch can transition between a conductive state where the communication section is electrically connected to the power reception antenna and a cut-off state where the communication section is electrically disconnected from the power reception antenna. The switch control section performs transition of the switch into the cut-off state when the direct current voltage exceeds a first threshold. The switch control section performs transition of the switch into the conductive state when the direct current voltage falls below a second threshold different from the first threshold.

The invention claimed is: 
     
       1. A power reception device comprising:
 a power reception antenna used for both communication and electric power reception; 
 a rectifier circuit connected to the power reception antenna, wherein the rectifier circuit converts, into direct current voltage, electric power received by the power reception antenna, and the direct current voltage is output; 
 a communication section which communicates via the power reception antenna; 
 a switch circuit connected between the power reception antenna and the communication section, wherein the switch circuit is transitable between a conductive state in which the communication section is electrically connected to the power reception antenna and a cut-off state in which the communication section is electrically disconnected from the power reception antenna; and 
 a switch control section connected to the rectifier circuit, wherein the switch control section performs transition of the switch circuit into the cut-off state when the direct current voltage output from the rectifier circuit exceeds a first threshold in association with start of the electric power reception by the power reception antenna, and the switch control section performs transition of the switch circuit into the conductive state when the direct current voltage falls below a second threshold different from the first threshold, 
 wherein the power reception device is configured such that when the power reception antenna starts the electric power reception, the direct current voltage output from the rectifier circuit rises to reach a maximum value of voltage output from the rectifier circuit, at which the direct current voltage output from the rectifier circuit is not supplied to a load, and subsequently lowers to a supplied value of voltage output from the rectifier circuit, which is smaller than the maximum value and at which the direct current voltage output from the rectifier circuit is supplied to the load, and 
 wherein: 
 the first threshold is larger than the supplied value and smaller than the maximum value; 
 the switch circuit includes an in-line switch and a ground switch; 
 the in-line switch is connected in series between the power reception antenna and the communication section; and 
 the ground switch is connected between a connection point, which is between the power reception antenna and the communication section, and ground. 
 
     
     
       2. The power reception device as recited in  claim 1 , wherein the second threshold is smaller than the supplied value. 
     
     
       3. The power reception device as recited in  claim 1 , wherein the power reception device further comprises a DC-DC converter connected between the rectifier circuit and the load. 
     
     
       4. The power reception device as recited in  claim 1 , wherein each of the in-line switch and the ground switch is formed of an N-channel FET. 
     
     
       5. An electronic apparatus comprising:
 a load; 
 a power reception antenna used for both communication and electric power reception; 
 a rectifier circuit connected to the power reception antenna, wherein the rectifier circuit converts, into direct current voltage, electric power received by the power reception antenna, and the direct current voltage is output; 
 a communication section which communicates via the power reception antenna; 
 a switch circuit connected between the power reception antenna and the communication section, wherein the switch circuit is transitable between a conductive state in which the communication section is electrically connected to the power reception antenna and a cut-off state in which the communication section is electrically disconnected from the power reception antenna; and 
 a switch control section connected to the rectifier circuit, wherein the switch control section performs transition of the switch circuit into the cut-off state when the direct current voltage output from the rectifier circuit exceeds a first threshold in association with start of the electric power reception by the power reception antenna, and the switch control section performs transition of the switch circuit into the conductive state when the direct current voltage falls below a second threshold different from the first threshold, 
 wherein the electronic apparatus is configured such that when the power reception antenna starts the electric power reception, the direct current voltage output from the rectifier circuit rises to reach a maximum value of voltage output from the rectifier circuit, at which the direct current voltage output from the rectifier circuit is not supplied to the load, and subsequently lowers to a supplied value of voltage output from the rectifier circuit, which is smaller than the maximum value and at which the direct current voltage output from the rectifier circuit is supplied to the load, and 
 wherein: 
 the first threshold is larger than the supplied value and smaller than the maximum value; 
 the switch circuit includes an in-line switch and a ground switch; 
 the in-line switch is connected in series between the power reception antenna and the communication section; and 
 the ground switch is connected between a connection point, which is between the power reception antenna and the communication section, and ground.